You're right that China has security checks for trains but I don't consider them comparable to flying. The train security checks are much faster. I've rarely had to wait more than 5 minutes in line. You don't have to take off your shoes, don't have to take out laptops and things from your luggage, and drinks and liquids are generally allowed. I've only on a couple occasions been asked by security in China to take a sip of an already-opened drink or reusable water bottle to prove that it's a drink.

The more annoying thing about rail in China is that many of the newer high speed rail stations are being built slightly outside of cities, and it often takes an extra hour to get to the station. Most of Europe's train stations are smack in the middle of downtown.